More efficient novel catalyst structures and catalyst support structures for heterogeneous catalysis are more and more meaningful considering the growing energy cost. The composition of the active substance is essential for the efficiency of catalyst structure, but its surface area and accessibility of the surface are also important. It is not easy to secure these two properties. Except for the final macro-shape, which is created for instance by pelletization, it is the inner structure, its porosity and the geometrical configuration of particles that have an impact on the surface accessibility.
The choice of the proper catalyst support structure often plays a crucial role especially in the case where the creation of a chemical bond between the carrier and the catalyst is necessary. For example this is the case of the system of SiO2 or TiO2 (supporting structure) and MoO3 (catalyst).
The synthesis problems and the thermal resistance of the catalyst structure are often important factors limiting its usability. The preparation or application of a catalyst often requires relatively high temperatures at which the structure can sinter, densify, lose the specific surface area, moreover an undesirable chemical reaction between the catalyst support structure and the catalyst can occur.
The TiO2 nanoparticles in the hydrated or anatase form are especially sensitive to the thermal cycles exceeding 300° C.
Despite the attractiveness of the TiO2 anatase catalyst structures, their preparation using the sulfate process, i.e. hydrolysis of TiOSO4 creating the titanium hydrate of the composition approximately Ti(OH)4, which is consecutively calcined, has serious drawbacks, such as the poor heat resistance accompanied by the fast loss of the specific surface area during the heat exposure and finally the crystal phase transformation into rutile. Materials prepared by the sulfate process often show a high content of residual hydrate and sulfur, which don't disappear even at temperatures exceeding 450° C.